Ultra-high strength alloys with good ductility are ideal materials for lightweight structural application in various industries. However, improving the strength of alloys frequently results in a reduction in ductility, which is known as the strength-ductility trade-off in metallic materials. Current alloy design strategies for improving the ductility of ultra-high strength alloys mainly focus on the selection of alloy composition (atomic length scale) or manipulating ultra-fine and nano-grained microstructure (grain length scale). The intermediate length scale between atomic and grain scales is the dislocation length scale. A new alloy design concept based on such dislocation length scale, namely dislocation engineering, is illustrated in the present work. This dislocation engineering concept has been successfully substantiated by the design and fabrication of a deformed and partitioned (D&P) steel with a yield strength of 2.2 GPa and an uniform elongation of 16%. In this D&P steel, high dislocation density can not only increase strength but also improve ductility. High dislocation density is mainly responsible for the improved yield strength through dislocation forest hardening, whilst the improved ductility is achieved by the glide of intensive mobile dislocations and well-controlled transformation-induced plasticity (TRIP) effect, both of which are governed by the high dislocation density resulting from warm rolling and martensitic transformation during cold rolling. In addition, the present work proposes for the first time to apply such dislocation engineering concept to the quenching and partitioning (Q&P) steel by incorporating a warm rolling process prior to the quenching step, with an aim to improve simultaneously the strength and ductility of the Q&P steel. It is believed that dislocation engineering provides a new promising alloy design strategy for producing novel strong and ductile alloys.

High strength-to-weight ratio, commendable biocompatibility and excellent corrosion resistance make Ti alloys widely applicable in aerospace, medical and marine industries. However, these alloys suffer from serious biofouling, and may become vulnerable to corrosion attack under some extreme marine conditions. The passivating and biofouling performance of Ti alloys can be attributed to their compact, stable and protective films. This paper comprehensively reviews the passivating and biofouling behavior, as well as their mechanisms, for typical Ti alloys in various marine environments. This review aims to help extend applications of Ti alloys in extremely harsh marine conditions.

The density of liquid Inconel 718 alloy was experimentally measured by electrostatic levitation technique, where the maximum undercooling of 100 K was realized for the commercial sample. The measured density of liquid Inconel 718 alloy is 7.39 g cm-3 at the liquidus temperature of 1663 K which was confirmed by DSC experiment, with the linear temperature coefficient of -6.89 × 10-4 g cm-3 K-1. Correspondingly, four ternary Ni-Cr-Fe compositions were designed to simulate the density of liquid Inconel 718 alloy with 16000 atoms, from which the liquid structure is revealed by pair distribution function. The predicted result shows a remarkable enhancement with the decrease of temperature at the first neighbor distance.

High-performance metal additive manufacturing (AM) has been extensively investigated in recent years because of its unique advantages over traditional manufacturing processes. AM has been applied to form complex components of Ti, Fe or Ni alloys. However, for other nonferrous alloys such as Al alloys, Mg alloys and Cu alloys, AM may not be appropriate because of its melting nature during processing by laser, electron beam, and/or arc. Cold spraying (CS) has been widely accepted as a promising solid-state coating technique in last decade for its mass production of high-quality metals and alloys, and/or metal matrix composites coatings. It is now recognized as a useful and powerful tool for AM, but the related research work has just started. This review summarized the literature on the state-of-the-art and problems for CS as an AM and repairing technique.

A facile ammonium-dichromate solution immersion method was introduced to synthesize the copper-wettable Cr3C2 coating on and inside the carbon-carbon (C/C) preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140° to 60°, demonstrating the significant improvement in the wettability. The Cr3C2-coated C/C-Cu composite with only 4.2% porosity and 3.69 g cm-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.

Polycrystalline Cr2AlC coatings were prepared on M38G superalloy using a two-step method consisting of magnetron sputtering from Cr-Al-C composite targets at room temperature and subsequent annealing at 620 °C. Particularly, various targets synthesized by hot pressing mixture of Cr, Al, and C powders at 650-1000 °C were used. It was found that regardless of the phase compositions and density of the composite targets, when the molar ratio of Cr:Al:C in the starting materials was 2:1:1, phase-pure crystalline Cr2AlC coatings were prepared by magnetron sputtering and post crystallization. The Cr2AlC coatings were dense and crack-free and had a duplex structure. The adhesion strength of the coating deposited on M38G superalloy from the 800 °C hot-pressed target and then annealed at 620 °C for 20 h in Ar exceeded 82 ± 6 MPa, while its hardness was 12 ± 3 GPa.

Carbon nanotube (CNT) arrays were fabricated on Ct-Me-N-(O) alloys with content of Ct in the range of 6-40 at.% by chemical vapour deposition. The Ct was a catalytic metal from the group of the following elements: Ni, Co, Fe, Pd, while Me was a transition metal from the group of IV-VII of the periodic table (where Me = Ti, V, Cr, Zr, Nb, Mo, Ta, W, Re). Carbon nanotubes were found to grow efficiently on the alloy surface with its composition containing Ti, V, Cr, Zr, Hf, Nb or Ta. The growth of CNTs was not observed when the alloy contained W or Re. Additions of oxygen and nitrogen in the alloy facilitated the formation of oxynitrides and catalyst extrusion on the alloy surface. Replacement of the metals in alloy composition affected the diameter of the resulting CNTs. The obtained results showed that the alloy films of varying thickness (10-500 nm) may be used for the CNTs growth. The resulting CNT material was highly homogenous and its synthesis reproducible.

Amelogenin isoforms constitute the predominant component in the enamel matrix and each amelogenin isoform executes unique role in the enamel biomineralization process. Enamel matrix derivative enriching amelogenin isoforms have also bioactive property for tissue regeneration. Despite the development of recombinant protein technology that has greatly forwarded the understanding of amelogenin properties, substantial evidences have revealed biochemical and functional difference between natural amelogenins and their recombinant form. To facilitate the study of enamel formation mechanism, more facile methodology to purify multiple natural amelogenin isoforms is pursued. Here we developed an effective one-shot method via reverse phase high-performance liquid chromatography (RP-HPLC) to purify various amelogenin isoforms from pig-derived amelogenin complex. A thorough process of chromatographic condition establishment including sample analysis on analytical scale and chromatographic condition design on preparative scale was described. Three representative amelogenin isoforms (TRAP, P148, P173) were isolated in one step and their purity was confirmed by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and high resolution mass spectrometry.

In this communication, we report the results of the studies on electrical properties of Zn0.95Cr0.05O nanoparticles synthesized using sol-gel method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements were performed for the structural and microstructural behaviors of the nanoparticles. Rietveld analysis was carried out to confirm the single phasic nature. High resolution TEM (HRTEM) confirms the nanoscale nature and polycrystalline orientations in the samples. Dielectric response has been understood in the context of universal dielectric response (UDR) model along with the Koop’s theory and Maxwell - Wagner (M-W) mechanism. Variation in ac conductivity with frequency has been discussed in detail in terms of power law fits. Results of the impedance measurements have been explained on the basis of crystal cores and crystal boundary density. Cole - cole behavior has been studied for the impedance data. For potential application of nanoparticles, average normalized change (ANC) in impedance has been estimated and discussed in the light of size effects and oxygen vacancies.

The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol (PVA) as binder by spray granulation method. The electromagnetic parameters of Fe and C composite particles were analyzed by vector network. The complex permittivity and magnetic permeability of Fe and C composite particles matched well with increasing C nanoparticle content, and then the microwave loss property was improved. A minimum reflection loss (RL) of -42.7 dB at 3.68 GHz for a composite with 4.6 mm in thickness can be obtained when the content ratio of the C nanoparticles, the modified Fe nanoparticles and the PVA is 21:49:30 (Sample 3).

The effect of particle shape on the porosity and compressive strength of porous hydroxyapatite (HA) scaffolds was investigated by sintering the mixture of rod-shaped HA (r-HA) and spherical HA (s-HA) with polyacrylamide used as the sacrificial template. It was found, for the first time, that addition of r-HA into s-HA could exponentially decrease the porosity of sintered HA scaffolds and enhance their compressive strength with the increase of r-HA content. The mechanism, according to the results from scanning electron microscopy and X-ray diffraction, lies in the restriction of s-HA to the grain formation and growth of r-HA during sintering and results in the fusion of r-HA with s-HA. These findings suggest that mixture of r-HA and s-HA might provide a new and facile way to improve the compressive strength of porous HA scaffolds.

Leaf extract of medicinally important plant Ocimum sanctum (O. sanctum) has been used for the synthesis of nickel nanoparticles (NiGs) and extraction of quercetin (Qu). Qu has been conjugated with NiGs for enhanced anticancer effect on human breast cancer MCF-7 cells. Extracted Qu was conjugated with polyethylene glycol (PEG) coated NiGs (Qu-PEG-NiGs) which was used as carriers for breast cancer treatment. Anticancer activity of Qu-PEG-NiGs was evaluated by assessing cell viability, reactive oxygen species (ROS) production, caspase activity, mitochondrial membrane potential (MMP) and changes in nuclear morphology (staining methods). 0.85 mg of quercetin was extracted from 1 g of leaves with retention time (Rt) of 2.914 min. Loading and encapsulation efficiency of quercetin onto PEG-NiGs was 15.04% and 82% respectively and Qu-PEG-NiGs has shown a sustained release of Qu of about 84% after 48 h. Qu and Qu-PEG-NiGs showed dose dependent (1.56-50 μg/mL) anticancer effect against MCF-7 cells with IC50 values of 50 and 6.25 μg/mL respectively which was mediated by oxidative stress due to ROS over-production that induced loss of mitochondrial membrane potential, capsase -9, -7 activities leading to apoptosis. The present study validates that Qu-PEG-NiGs can be used as a potential anticancer agent for cancer therapy.

In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu (hereafter named as Co-Cu) alloy was studied in this paper at a deformation temperature range of 950-1150 °C and a strain rate range of 0.008-5 s-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electrochemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature (1100-1150 °C) would reduce the corrosion resistance slightly. The final optimized deformation process was: a deformation temperature from 1050to 1100 °C, and a strain rate from 0.008 to 0.2 s-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.

Effects of trace addition of Ag on the fatigue crack propagation behavior and microstructure of a medium-strength aged Al-Zn-Mg alloy were investigated in the present work. The results show that a combination of enhanced tensile strength and improved fatigue crack propagation resistance in Al-Zn-Mg alloys is achieved with small addition of Ag. The enhanced strength is attributed to the high density of η′ precipitates within the grains and narrow precipitate free zones in the vicinity of grain boundaries. The main contribution to the improvement of fatigue crack propagation resistance comes from the coarser precipitates within the grains. When subjected to two-step aging, Ag-added alloy shows larger semi-coherent matrix precipitates. These relatively coarser precipitates increase the homogeneity of deformation and therefore improve the fatigue crack propagation resistance. In addition, microstructure analysis indicates that the size and distribution of inclusions as well as the grain structures of Al-Zn-Mg alloys are independent of Ag addition.

Differential scanning calorimetry (DSC) analysis, isothermal solidification experiment and Thermo-Calc simulation were employed to investigate solidification characteristics of K417G Ni-base superalloy. Electron probe microanalysis (EPMA) was employed to analyze the segregation characteristics. Liquidus, solidus and the formation temperatures of main phases were measured. In the process of solidification, the volume fraction of liquid dropped dramatically in the initial stage, while the dropping rate became very low in the final stage due to severe segregation of positive segregation elements into the residual liquid. The solidification began with the formation of primary γ. Then with solidification proceeding, Ti and Mo were enriched in the liquid interdendrite, which resulted in the precipitation of MC carbides in the interdendrite. Al accumulated into liquid at the initial stage, but gathered to solid later due to the precipitation of γ/γ′ eutectic at the intermediate stage of solidification. However, Co tended to segregate toward the solid phase. In the case of K417G alloy, combining DSC analysis and isothermal solidification experiment is a good way to investigate the solidification characteristics. Thermo-Calc simulation can serve as reference to investigate K417G alloy.

The microstructure and mechanical properties of pulse metal inert-gas (MIG) welded dissimilar joints between 4 mm thick wrought 6061-T6 and cast A356-T6 aluminum alloy plates were investigated. The tensile strength of the joints reached 235 MPa, which is 83% of that of 6061 aluminum alloy, and then decreased with the increase of travel speed while keeping other welding parameters constant. The microstructure, composition and fractography of joints were examined by the optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Grain boundary liquation and segregation occurred in the partially melted zone (PMZ) on 6061 aluminum alloy side, and brittle Fe-rich phases were observed in partially melted zone on A356 aluminum alloy side. The minimum microhardness appeared in heat-affected zone (HAZ) near A356 aluminum alloy substrate. The samples during tensile test failed mainly in PMZ and HAZ on A356 aluminum alloy side through mixed fracture mode with quasi cleavage and dimples on fracture surface.

The oxide films formed on Alloy 690 exposed to 600 °C supercritical water were characterized using mass measurement, X-ray diffraction, Raman spectroscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It was found that the mass gain of the alloy in supercritical water decreased with increasing exposure time. The oxide films have a double-layer structure, with an inner layer rich in Cr and outer layer rich in Ni and Fe after short time and long time exposure. The penetration of the oxide along the grain boundaries was observed, and the penetration depth increased with increasing exposure time. The grain boundaries and voids are the short-path of oxygen diffusion into the metal.

Electron beam welding (EBW) was applied to a 10-mm-thick plate cut from Ti-6246 compressor disk. The microstructural characteristics, microhardness and room temperature tensile properties were investigated. Microstructure observations indicated that there existed plenty of thin needle-like α platelets studding in the matrix of the columnar β grains in the as-welded fusion zone (FZ). Post-weld heat treatment (PWHT) led to the precipitation of small secondary α platelets in the β matrix in heat affected zone and FZ. The thickness and the density of α platelets increased as the temperature of PWHT increased from 545 to 645 °C. The microhardness across the Ti-6246 EBW joint exhibited a nonuniform distribution. The hardness increased with the decrease of distance to the weld center, and reached the maximum of 467 HV in FZ when PWHT was carried out at 595 °C. All the weldments tested with tension were fractured at the base material (BM) and exhibited a ductile fracture mode. The major deformation barrier in BM was the platelet α/β interfaces, however, the major deformation barrier in FZ was found to be β grain boundaries and secondary α/β interfaces. The BM with thicker platelet α phases had lower strength than the other two zones in the joint, and the BM deformed first and led to fracture in this zone.